In the E-UTRAN (Evolved Universal Terrestrial Radio Access Network), the data is transmitted via the uplink shared channel. The BS (Base Station) allocates resources for each UE (User Equipment). In order to allocate resources and to provide service to each UE according to its own need so as to realize better multiplexing performance in uplink transmission, the BS needs to know how many resources it should allocate to each UE; therefore the UEs need report their own requirements to the BS in an efficient way. The reporting scheme of scheduling information, which supports uplink group scheduling, is an important feature defined in the progress of LTE (Long Term Evolution) standardization.
The following issues need to be considered during the design of the report of scheduling information:
1. The Scheduling Information should Provide Sufficient Information to Increase the Efficiency of Scheduling
In the prior wireless data telecommunication system, resource allocation usually applies the following two methods: buffer-aware algorithm and buffer-blind algorithm. Compared with the buffer-blind algorithm, the buffer-aware algorithm can increase the efficiency of scheduling since it carries out the scheduling on the basis of the buffer size information reported by the UE, while the buffer-blind algorithm schedules only according to the usage status of the resources allocated in the past. Therefore, buffer report, i.e., buffer size report is the important scheduling information required to be reported. And due to the fact that all the services of QoS in LTE are transmitted via shared channel, it requires the BS to provide efficient scheduling and to satisfy the requirement of latency and packet error, thus the latency information is also required to be reported to the BS by the UEs. This requires a well defined efficient reporting scheme for latency information.
2. The Scheduling Information should Support Qos-Aware Scheduling
To support QoS-aware scheduling, the report of scheduling information should be differentiated according to different QoS.
3. The Overhead of Scheduling Information should be as Few as Possible
The overhead of scheduling information should be as few as possible because the amount of the overhead influences the uplink capacity directly.
So far, there have been several reporting schemes of scheduling information. Reference 1 (R2-068029, Buffer Reporting for E-UTRAN, ETRI, Athens, Greece, 27-31 Mar. 2006) only discussed the method of buffer report. Although it supports the buffer report method based on priority, the format of report includes the buffer information of all service streams and the size of the format of report is fixed. Reference 2 (R2-061023, Timer-based Resource Request, ETRI, Athens, Greece, 27-31 Mar. 2006) discussed different content and mechanism of report for different services, but the descriptions were rough and didn't propose detailed format of report.
Reference 1 only discussed buffer report without report of latency information. Reference 2 proposed the concept of head of line (HOL) delay, but it is the reporting method for absolute latency information.
In HSUPA (High Speed Uplink Packet Access) system, the report information is transmitted via scheduling information and happy bit. The scheduling information is transmitted via MAC signaling, and it comprises the overall buffer size and buffer length of the logic channel with the highest priority. This kind of reporting method could not differentiate the priority of service with low priority; therefore, the scheduling based on priority could not be supported. Furthermore, the signaling overhead is relatively high due to the frequent reports. The happy bit is used only for indicating the satisfactory for the present allocated resource, but could not indicate the latency information and packet loss information.